1. Field of the Invention
The present invention relates to a control technique of an image capturing apparatus that switches so that a live image or a composite image composed of images, each of which has a short exposure time, is displayed.
2. Description of the Related Art
In recent years, image capturing apparatuses such as digital cameras have been proposed that generate a single composite image composed of multiple images and provide this to the user. A first object of generating a composite image is for expanding the dynamic range. In other words, this is because by varying the exposure while capturing multiple images and composing images having different exposures, it is possible to generate an image having little highlight-detail loss (overexposure) and shadow-detail loss (underexposure) and a wide dynamic range. A second object is greater high-sensitivity. This is because by composing multiple images, the (random) noise component contained in the image is suppressed and the SN ratio of the composite image can be improved.
A point of caution when generating the above-mentioned composite image is that, depending on the object and capture conditions, the composite image can engender a visual sense of strangeness (unnaturalness). Furthermore, in composing the images it is necessary to compose after correcting positional shifting produced between the multiple images, but sometimes this positional shifting cannot be corrected sufficiently depending on the object or the capture conditions such that a blurred image is generated. In this way, sometimes the composite image is undesirably different from the image intended by the user.
For example, Japanese Patent Laid-Open No. 2009-088927 has optimal internal settings for a normal shooting mode (not performing image composing) and a composite image mode, and provides optimal image quality with these modes.
However, optimal settings do not necessarily match the user's preferences and in this case the user will be required to experiment twice with the normal shooting mode and with composite image shooting. Or embodiments are conceivable in which, depending on the product, shooting is performed automatically with the normal shooting mode and image composing with a one-time shutter release, thereby allowing the user to select afterward.
Either way, since the composite image cannot be confirmed until after shooting (after shutter release), it will be desirable for the user to be able to easily confirm the composite image on the display unit prior to actual shooting.
However, problems occur also in cases where the composite image is always displayed prior to shooting. For example, as shown in FIG. 3, with composite images during panning or zooming, depending on the conditions, sometimes a portion of the composite image will become dark or blurred. Accordingly, since zooming and panning often occurs while the user adjusts the composition or angle of view prior to shooting, displaying a single image without displaying a composite image is better for the tracking characteristics of the displayed image for motion and is preferable for the purpose of adjusting the composition and the angle of view.
On the other hand, after the user has finished panning or zooming and immediately prior to shooting, it is preferable to display the composite image so as to enable a finished composite image to be confirmed prior to shooting.